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EDAITUTOR
ED Reference · Anaphylaxisv0.1 · adult & paedsEducational use only
Anaphylaxis
A clinical diagnosis — IM adrenaline first, adrenaline early. One brief, two populations: switch between adult and paediatric dosing and pathways.
Give IM adrenaline into the anterolateral thigh the moment anaphylaxis is recognised — do not wait for IV access, hypotension, a rash, antihistamines, steroids or investigations. There is no absolute contraindication to IM adrenaline in life-threatening anaphylaxis (not age, hypertension, cardiac disease or pregnancy). Lay the patient flat; sudden standing or sitting can be fatal. Repeat every 5 minutes if compromise persists.
Full interactive decision pathway
Step-through adultpaediatric anaphylaxis on ED AI Tutor Clinical Pathways — recognition → adrenaline → ABCDE → refractory → disposition.
IV/IO access — but never delay adrenaline to get it
🟢 doseAdult: adrenaline 0.5 mg IM (0.5 mL of 1 mg/mL), repeat q5min.Paeds: 0.01 mg/kg IM of 1:1000 (max 0.5 mg), repeat q5min — see calculator below.
🟢 ANZCOR · RCHEM Cases
IM Adrenaline — first-line, life-saving
Adult dosingPaediatric dosing
Adult IM dose · 1 mg/mL (1:1000)0.5 mg= 0.5 mL IM, mid-anterolateral thigh
Repeat every 5 minutes while airway, breathing or circulatory compromise persists. Adults ≥50 kg receive the full 0.5 mg. The thigh beats deltoid or subcutaneous — faster, more reliable absorption.
SafetyNo absolute contraindication
Do not reduce or withhold for age, hypertension or coronary disease. IV adrenaline boluses are NOT routine initial treatment — far greater medication-error and arrhythmia risk. Do not use subcutaneous adrenaline.
⚪ pitfallUnder-dosing kills. A single 0.3 mg auto-injector may deliver only a fraction of the weight-based dose in a heavy adult — draw up the full 0.5 mg from the ampoule with a 1 mL syringe.
Paediatric IM dose · 1:10000.01 mg/kg= 0.01 mL/kg · max 0.5 mg (0.5 mL)
Anterolateral thigh, repeat every 5 minutes if symptoms persist. In a child with anaphylaxis and known asthma, always give adrenaline first, then asthma medications.
Measurement safetyBeware < 0.1 mL
Volumes under 0.1 mL are hard to measure and prone to 10× overdose under stress. Use a 1 mL syringe. Do not use subcutaneous adrenaline (unreliable absorption).
Paediatric adrenaline & fluid calculator
Enter actual weight. Deterministic — 0.01 mL/kg of 1:1000 (max 0.5 mL) and 20 mL/kg crystalloid. Always cross-check against the RCH chart below and local guidelines.
kg
IM adrenaline 1:1000
— mL
anterolateral thigh · repeat q5min
Fluid bolus (if shocked)
— mL
20 mL/kg isotonic crystalloid · reassess & repeat
Adrenaline infusion start
— mL/hr
1 µg/mL mix · 5 mL/kg/hr ≈ 0.1 µg/kg/min
Infusion recipe (RCH, non-tertiary): 1 mL of 1:1000 adrenaline in 1000 mL sodium chloride 0.9% ≈ 1 µg/mL; start 5 mL/kg/hr; dedicated line, pump, anti-reflux valve; titrate; avoid high rates >2 hr; continuous vitals, 12-lead ECG and conscious-state monitoring. Follow local infusion guidelines and senior/retrieval advice.
Age (yrs)
Weight (kg)
Adrenaline 1:1000 (mL)
Auto-injector device
<1
<7.5
0.1 *
Not available
1–2
10
0.1
EpiPen Jr 150 µg (7.5–20 kg, <5 yrs)
2–4
15
0.15
4–5
20
0.2
5–10
30
0.3
EpiPen 300 µg (>20 kg, ≥5 yrs)
10–12
40
0.4
>12
>50
0.5
Anapen 500 µg (>50 kg, >12 yrs)
🔴 note* Volumes <0.1 mL are difficult to measure accurately and prone to 10× overdose — RCH gives a minimum of 0.1 mL in the smallest infants.
High-flow O₂ · call an experienced airway clinician early
Prepare for a difficult airway; consider early controlled intubation if swelling progresses
Nebulised adrenaline may temporise upper-airway oedema — never replaces IM
CICO → FONA ready
B
Breathing
Oxygen for hypoxaemia; monitor RR and SpO₂
Salbutamol for persistent bronchospasm after adrenaline
Bronchodilators do not treat oedema, vasodilatation, capillary leak or shock
Persistent systemic features → keep repeating IM adrenaline
Adrenaline > salbutamol
C
Circulation
Cardiac monitoring · frequent BP · large-bore IV or IO
Bolus 500–1000 mL warmed crystalloid for hypotension
Bolus 20 mL/kg isotonic crystalloid if shocked
Reassess and repeat — severe shock may need several boluses
Do not delay IM adrenaline to obtain access
SBP <90 = shock20 mL/kg, repeat
D/E
Disability / Exposure
Assess conscious state; watch for deterioration
Expose to find the trigger (sting, patch, infusion) and stop ongoing exposure
Reassess after every adrenaline dose
Escalate early if not improving
Reassess q5min
⚪ keyAnaphylaxis causes profound vasodilatation and rapid intravascular volume loss — adrenaline + fluids together. Salbutamol, antihistamines and steroids do not reverse shock.
Refractory anaphylaxis
AdultPaediatric
🔴 definitionAnaphylaxis needing ongoing treatment for persisting respiratory or cardiovascular compromise despite 2 appropriately-dosed, correctly-given IM adrenaline doses, correct positioning, oxygen and adequate fluids.
IV adrenaline infusion
Monitored resus only
Escalate to a titratable IV adrenaline infusion per local critical-care protocol after 2 IM doses fail. Infusion pump, labelled standard concentration, continuous ECG/BP/SpO₂; consider arterial line in profound shock.
Peripheral infusion (RCH, non-tertiary): 1 mL 1:1000 in 1000 mL saline (≈1 µg/mL), start 5 mL/kg/hr (≈0.1 µg/kg/min); dedicated line, pump, anti-reflux valve; titrate; avoid high rates >2 hr.
Experienced clinicians
Avoid IV boluses
Peri-arrest only
Routine IV boluses cause hypertension, dysrhythmia and ischaemia. Small boluses only by experienced resuscitationists as a peri-arrest bridge.
IV bolus not recommended; in peri-arrest, adrenaline 1 µg/kg IV per resuscitation resources.
High error risk
Persistent vasoplegia
Add support
Continue reassessed crystalloid. Add a second vasopressor if shock persists despite adequate adrenaline infusion. Seek ICU early; bedside ultrasound for ventricular function and competing shock causes.
ICU / retrieval
On a beta-blocker?
Glucagon
Persistent hypotension/bradycardia despite adrenaline → consider IV glucagon under senior critical-care guidance. Anticipate vomiting/aspiration and hyperglycaemia.
Senior-led
Reassess the diagnosis
Not improving?
Check dose/site, ongoing exposure — then tension pneumothorax, severe asthma, PE, sepsis, cardiogenic shock, haemorrhage, isolated angioedema.
Wrong dose/site?
Chest pain — Kounis
Allergic ACS
Mediator-driven coronary vasospasm, plaque rupture or stent thrombosis. Treat the anaphylaxis and the ACS together; correctly-dosed IM adrenaline stays indicated when severe.
Treat both
Escalate & retrieve
>2 doses / infusion
Seek expert critical-care / paediatric transport advice for >2 doses or an infusion. Consider transfer for care beyond local capability — PIPER for paediatric retrieval in Victoria.
PIPER · confirm locally
Reassess the diagnosis
Not improving?
Check adrenaline dose and injection site, ongoing allergen exposure, and consider severe asthma or an alternative cause of shock.
Wrong dose/site?
AMAX4 — the crashing patient Hard deck · 4 minutes
For the unconscious or peri-arrest anaphylaxis/asthma patient (adult or child), time to hypoxic brain injury is about 4 minutes. Most young people with anaphylaxis die from bronchospasm. Prioritise first-pass oxygenation: RSI to a cuffed ETT — supraglottic devices and bag-valve-mask cannot overcome the very high airway pressures (50–100 cmH₂O) of severe bronchospasm. Use a paralytic, video laryngoscopy and the best intubator in the room; declare can't-intubate-can't-oxygenate early and be ready for surgical front-of-neck access. Keep giving IM/IV adrenaline throughout.
⚪ AMAX4 algorithm — Dr Ben McKenzie · amax4.com/algorithm · see also LITFL & EM Cases Ep 187
Adjuncts — not first-line
Antihistamines — may ease itch, urticaria, flushing; do not treat airway oedema, bronchospasm or shock
Corticosteroids — delayed onset; do not reverse acute compromise; no proven prevention of biphasic reactions
Neither must ever delay adrenaline
Give antihistamines only after adrenaline and resuscitation, once stable — non-sedating oral preferred
Reserve steroids for a separate indication (e.g. persistent asthma / protracted bronchospasm)
⚪ evidenceNo demonstrated mortality benefit from H1/H2 antihistamines or steroids. RCH: antihistamines, corticosteroids and leukotriene antagonists should not be given in acute anaphylaxis.
🟢 ANZCOR · RCHEM Cases · LITFL
Investigations
Clinical diagnosis — investigations must never delay treatment
Guided by severity: ECG, VBG/ABG, lactate, electrolytes/renal, glucose
Troponin if chest pain, ECG changes or significant cardiac disease (think Kounis)
Usually none required in children
Serum tryptase only where the diagnosis is genuinely uncertain / atypical, per local timing
⚪ tryptaseA normal tryptase does not exclude anaphylaxis (often normal in food-triggered reactions). If sent: baseline after resuscitation begins, ~1–2 h, and ~24 h / at follow-up.RCH: no role in acute management; only in significant diagnostic doubt or with allergy-specialist input.
🟢 RCH · ASCIAEM Cases · LITFL · ASCIA
Observation & disposition
AdultPaediatric
Minimum 4 hours
Lower-risk
Shorter observation
All children observed in a setting able to manage deterioration for at least 4 hours after the last adrenaline dose (or after symptom onset if none given).
Shorter monitored observation may suit prompt resolution after one IM dose, normal vitals, no severe asthma, no ongoing absorption, and reliable access to care + autoinjectors.
Prolonged / admit
Higher-risk
>1 (paeds: >2) adrenaline doses, adrenaline infusion or IV fluids; circulatory involvement; delayed adrenaline; severe respiratory compromise or significant hypotension; poorly-controlled asthma; previous biphasic/severe reaction; unknown trigger or ongoing absorption; isolated location; late-evening presentation.
Admit — monitored
Escalate
Persistent/recurrent symptoms, anaphylactic shock, airway intervention, adrenaline infusion, significant ischaemia/dysrhythmia, major comorbidity, or ongoing oxygen/bronchodilator/vasopressor need. Overnight admission per RCH criteria.
⚪ biphasicBiphasic reactions are uncommon but can follow apparent resolution; greater initial severity and delayed or repeated adrenaline increase the risk. Cardiorespiratory arrest >4 hours after exposure is rare.
Before discharge — every patient leaves equipped
Adrenaline autoinjector
If indicated
Prescribe/supply — commonly two devices. Check correct strength, demonstrate with a trainer, and have the patient/parent demonstrate back.
By weight: 150 µg 7.5–20 kg · 300 µg >20 kg · 500 µg >50 kg. PBS-available for children with a history of anaphylaxis. Drug-only anaphylaxis is generally not prescribed a device.
Adults: 300 µg or 500 µg per weight/availability. Prefer the strength closest to the weight-based dose.
Written action plan
ASCIA plan
Individualised ASCIA Action Plan for Anaphylaxis. Adrenaline immediately for recurrence, call an ambulance after use, and do not stand or walk suddenly afterwards.
Trigger & education
Avoidance
Document the suspected trigger; give avoidance advice and label-reading where relevant. Avoid broad, unverified allergy labels. Inform school/daycare and carers. Consider a MedicAlert.
Follow-up
Referral
GP follow-up and referral to allergy/immunology (paediatrician for children). Optimise asthma control and review cardiovascular medications where relevant.
⚪ resourceAllergy & Anaphylaxis Australia and ASCIA provide patient education, action plans and trainer resources. Severity of previous reactions does not predict future risk — safe discharge planning is essential.
Red flags — act / escalate now
Airway swellingTongue/throat swelling, stridor, hoarse voice, drooling → adrenaline now, early airway expert, prepare for CICO.
Isolated shockHypotension or collapse after a likely allergen with no rash — still anaphylaxis until proven otherwise.
2 doses, no betterRefractory anaphylaxis → IV adrenaline infusion, fluids, ICU/retrieval.
Crashing patientUnconscious or peri-arrest from bronchospasm → AMAX4: RSI to a cuffed ETT, 4-minute hard deck.
Sudden posture changeStanding, sitting up or walking during anaphylaxis can cause arrest — keep flat.
Chest painConsider Kounis syndrome — treat anaphylaxis and ACS together.
Known asthmaAdrenaline first, then asthma treatment — asthma raises fatality risk.
🟢 ANZCOR · RCH · ASCIA · EM Cases · LITFL · AMAX4
ED AI Tutor — ED Reference Series · v0.1 · For clinician education only. Not a substitute for clinical judgement, local guidelines or senior oversight. Adult and paediatric doses shown are guideline reference values — verify every dose before administration.
